RC-Monster Forums - Homemade USB Charging Station

My family has a bunch of devices which charge via USB in some form or another and many of our "power strips" are littered with all sorts of "wall warts" to charge these devices. So, I decided to make my own USB charging station consisting of 8 USB ports. Since many of todays devices can draw up to 2.1A, I designed this so each port can supply that level of current simultaneously. There are multi-port USB chargers on the market, but are can't usually provide that full current on all ports at once.

First, I picked up several USB port headers from Newegg.com. They are used is computers where there are extra USB headers on the motherboard and mount in an empty expansion slot.

Note: the brackets on these are designed for low-profile cases, so are shorter than a standard case expansion slot. This was intentional as I didn't want to have to cut the brackets down.

http://scriptasylum.com/forumpics/USB Charger/img_1.jpg

Next, I removed the plastic connectors, tied the shields and grounds together (which is acceptable according to the USB spec), tied the data+ and data- lines together (standard way of enabling hi-current charging), and added a 3A fuse on each port just in case of catastrophic failure. The device being charged will determine the current being drawn, but if something goes wrong with that device, the fuse will blow instead of the wires melting from over-current. Note: for charging crApple products, you have to do something different with the data+ and data- lines to activate fast charging mode. But I refuse to build anything that will be used with those devices.

The "fuse holders" are just some female quick-disconnect spade terminals - a trick I learned from my car-audio/alarm/remote start installation days.

http://scriptasylum.com/forumpics/USB Charger/img_2.jpg

Then, I scavanged one of my old ATX power supplies formerly being used as a 12v supply for battery chargers. Since I now use much higher current HP server supplies, the ATX supply wasn't being used. I had already modded it by shorting the green wire to ground (I used the switch on the supply to turn it on and off) and replacing the mass of wires with a single 12GA wire for the 12v line. So, I just had to add a set of 12GA wires for the 5v USB line. I also tweaked the output voltage (this supply has a convenient adjustment pot) to provide between 5.1v (no load) to 4.90v (loaded to ~18A), which is well withing the USB spec of 5v +/-5% (4.75v-5.25v).

http://scriptasylum.com/forumpics/USB Charger/img_3.jpg

http://scriptasylum.com/forumpics/USB Charger/img_4.jpg

Then, I built a box using some spare pieces of wood I had laying around from previous projects, and painted it using some textured paint (to hide any imperfections). And since I didn't have the specific color of textured paint I wanted, I applied a top coat of satin black.

The grate on the front is simply an intake for the power supply since it has an exhaust fan, and was made from an unused cut-up speaker grille.

The power supply was mounted using a Lian-Li power supply bracket I had in my parts bin (from an uncompleted project many years ago), which made it a bit easier.

http://scriptasylum.com/forumpics/USB Charger/img_5.jpg

http://scriptasylum.com/forumpics/USB Charger/img_6.jpg

http://scriptasylum.com/forumpics/USB Charger/img_7.jpg

Yeah, it's a mess of wires in there. Having 8 individually-fused ports creates quite a mass of wires, but everything is soldered well and heat-shrunk for safety. I even added a set of binding posts on the back for the 12v line in case I need it.

Once I got it all together, I hooked up as many USB devices as I could to see if it would work as advertised, and it was able to charge everything perfectly fine, even in "high-current" mode (where applicable). The list of devices I had all running:

- Kindle Fire tablet
- Samsung Galaxy Tab 2 7.0 tablet
- HTC Merge Android phone
- B&N Nook e-reader
- LG flip phone (not smart phone)

And to make sure these devices were pulling as much current as possible while charging, I had the tablets and my phone all running MP4 video streaming from my media server at the same time (video decoding is power hungry).

The only thing I had to buy were the USB brackets and 3 fuses (only had 5 of the 8 I needed), so this whole project set me back about $30 total. Yeah, several 2.1A chargers would take up less room, but would be more expensive and not as cool - not to mention I also have a "free" 12v 15A supply for whatever. :smile: